Night Lights Give You Cancer?
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|Scientists at the National Cancer Institute and National Institute of Environmental Health Sciences in the United States have been doing research that reveals that exposure to light at night is a significant cause of some types of cancer.
Sleeping with the light on or staying up late could be a cause of breast cancer, authoritative new research suggests.
The research - which is being hailed as a "watershed", providing "the first proof" of a link between artificial light at night and cancer - confirms a mass of the studies suggesting that modern life causes the disease by interfering with natural sleep cycles.
Carried out by the blue-chip National Cancer Institute and National Institute of Environmental Health Sciences in the United States, it offers a solution to the mystery of rising levels of breast cancer in rich countries, which are five times as high as in the developing world. One in 10 women will develop the disease.
Experts believe that half of the cancers are likely to be accounted for by family history, smoking, drinking alcohol, diet, medicines, and such reproductive factors as childlessness and having children late. But evidence has been building up that electric light during the hours of darkness may be responsible for much of the rest.
Repeated studies have shown that night-shift workers - such as nurses or air stewardesses - are up to 60 per cent more likely to get the disease. Another found that women who stayed up late two or three times a week were similarly susceptible. Conversely totally blind women are half as likely to succumb to it.
"If light were a drug, the government would not approve it," says Professor Charles Czeisler of the Harvard Medical School. And Professor George Brainard of Thomas Jefferson University in Philadelphia, adds: "Humans evolved on a planet without electric light over thousands and thousands of generations. The body is designed to be alert and awake during daytime hours and to sleep at night. Now we have a 24-7 society that isn't in harmony with our biological design."
Studies show that light at night interferes with one of the body's greatest natural defences against cancer - melatonin, dubbed "the hormone of darkness". The hormone - which is secreted by the pineal gland at night, and particularly in the early hours of the morning - both impedes the growth of cancers and boosts the immune system.